Two Different Interactions between Oxygen Vacancies and Dopant Cations for Ionic Conductivity in CaO-Doped CeO2 Electrolyte Materials

2000 ◽  
Vol 658 ◽  
Author(s):  
Yuanzhong Zhou ◽  
Xi Chen
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Electrical Measurement ◽  
Free Oxygen ◽  
Oxygen Ion ◽  
Association Energy ◽  
Defect Interactions

ABSTRACTThe electrical measurement has demonstrated that conductivity of CaO-doped CeO2 has higher activation energy for low temperature and lower activation energy for high temperature. A model with two different kinds of defect interactions between oxygen vacancy and doped cations has been used to interpret the phenomenon. Diffusion based on hopping of oxygen ions was assumed as the mechanism of electrical conduction. The analysis indicated that at high temperature free oxygen vacancies are dominant and the activation energy is only for oxygen ion hopping. At low temperature, however, oxygen vacancies associated with dopant calcium ions are dominant for high CaO content and the activation energy is the energy for hopping of an oxygen ion plus half of the association energy between one oxygen vacancy and one calcium ion. For low level doping, both free and associated oxygen vacancies are important.

Electrical properties of ultrafine-grained yttria-stabilized zirconia ceramics

1997 ◽  
Vol 12 (9) ◽  
pp. 2374-2380 ◽  
Author(s):  
Shusheng Jiang ◽  
Walter A. Schulze ◽  
Vasantha R. W. Amarakoon ◽  
Gregory C. Stangle
Keyword(s):  
Grain Size ◽  
Oxygen Vacancy ◽  
Grain Boundary ◽  
Oxygen Vacancies ◽  
Synthesis Process ◽  
Physical Parameters ◽  
Fine Grained ◽  
Oxygen Ion ◽  
Average Grain Size ◽  
Vacancy Concentrations

Nanoparticles of yttria-doped tetragonal zirconia polycrystalline ceramics (Y-TZP) with an average crystallite size of less than 9 nm were prepared by a combustion synthesis process. Dense and fine-grained (<200 nm) Y-TZP ceramics were obtained by fast-firing using temperatures lower than 1400 °C and dwell times of less than 2 min. Impedance spectroscopy was employed to measure conductivities of oxygen vacancies in the grain and the grain boundary of the fine-grained Y-TZP. The relationships between the concentration of the oxygen vacancies in the grain boundary and measurable physical parameters were determined semiquantitatively. The oxygen vacancy concentrations and activation energies for the oxygen-ion conduction in the grain and the grain boundary of the fine-grained Y-TZP were found to be independent of the average grain size in the average grain-size range of 90–200 nm. These experimental results suggest that, in order to retain the abnormally high oxygen vacancy concentrations of the Y-TZP nanoparticles and thus enhance the oxygen-ion conductivity, it may be necessary to decrease the average grain size to approximately 10 nm.

Phase Relations And Conductivity In ZrO2-Sc2O3-La2O3 System

1994 ◽  
Vol 346 ◽  
Author(s):  
Akihiko Yamaji ◽  
Takao Ishii ◽  
Masami Kanzaki
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Structural Transition ◽  
Ion Conductivity ◽  
Cubic Phase ◽  
Discontinuous Change ◽  
Ion Conductor ◽  
Oxygen Ion ◽  
Phase Stabilization ◽  
Oxygen Ion Conductor

ABSTRACTThe oxygen-ion conductor 0.88ZrO2-0.12Sc2O3 has a discontinuous change in ion conductivity at about 660°C. This change accompanies the structural transition from rhombohedral to cubic phase. Since the high temperature cubic phase shows large ion conductivity, it is of interest to examine whether or not the cubic phase stabilizes in the low temperature region by another dopant . By adding only 0.005 mole % La2O3, the cubic phase is stabilized below about 500 °C without any loss of conductivity compared with 0.88ZrO2-0.12Sc2O3. The ion conductivity of cubic stabilized ZrO2-Sc2O3-La2O3 system is around 1×10-1 S/cm at 800°C. Cubic phase stabilization using second dopant in a ZrO2-Sc2O3 system led to the finding of a fast oxygen-ion conductor in the ZrO2-Sc2O3-La2O3 system.

The mechanism of the Pinacol-Pinacone rearragement. VI. Low temperature kinetics

1957 ◽  
Vol 10 (2) ◽  
pp. 160 ◽  
Author(s):  
JF Duncan ◽  
KR Lynn
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Temperature Reaction ◽  
Hydrogen Ion Concentration ◽  
High Temperature Reaction ◽  
Stage Process ◽  
Low Temperature Kinetics

The low temperature rearrangement of pinacol to pinacone appears to be second order with respect to the hydrogen ion concentration. The activation energy is, however, similar to that of the high temperature reaction. This is interpreted as indicating that in the low temperature reaction the synartetic step is formed by a two stage process, through a stable intermediate, and each stage requires the participation of a hydrogen ion.

Non-isothermal thermogravimetric analysis of heavy oil in an O2/CO2 atmosphere

2018 ◽  
Vol 16 (6) ◽  
Author(s):  
Zhiqiang Wang ◽  
Ming Liu ◽  
Xingxing Cheng ◽  
Yusheng He ◽  
Yingjie Hu ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Low Temperature ◽  
Oxygen Concentration ◽  
Heavy Oil ◽  
Combustion Process ◽  
Molecular Weights ◽  
Diffusion Controlled ◽  
Temperature Activation

Abstract Although heavy oil is an abundant and promising energy source, its processing and utilization are complicated due to its high density, low hydrogen/carbon ratio, and high asphaltene content. Fortunately, these problems can be mitigated by the application of oxy-fuel combustion. To gain deeper insights into the above technology, the characteristics of heavy oil combustion in an O2/CO2 atmosphere was investigated using non-isothermal thermogravimetric analysis. We demonstrate that the combustion process consisted of four stages. Low-molecular-weight hydrocarbons reacted at low temperature, whereas heavy ones required a higher temperature. Increasing the concentration of oxygen resulted in increased TGA and DSC peak intensities and decreased peak widths, and these peaks were shifted to lower temperatures. Coat-Redfern and Flynn-Wall-Ozzawa methods were used to evaluate the kinetic parameters (E, A) of the oxidation process, showing that the high-temperature activation energy was much higher than the low-temperature one due to the different molecular weights of the oxidized substrates in each region. The reaction was demonstrated to be diffusion-controlled, as reflected by the lower activation energy at high oxygen concentration and high temperature, with the influence of oxygen concentration on QO processes being much more obvious than that on SO ones.

The Fushun Oil Shale Semi-Coke’s Combustion Features and Thermal Dynamic Analysis

2014 ◽  
Vol 694 ◽  
pp. 327-331
Author(s):  
Yan Chang Li ◽  
Yu Meng Yang
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Heating Rate ◽  
Oil Shale ◽  
Reaction Order ◽  
Ignition Point ◽  
Reaction Orders ◽  
Combustion Features ◽  
High Temperature Condition

This study analyses the Fushun oil shale semi-coke samples prepared in 450°C, 550°C and 650°C by using STA449 TGA. The experiment studied their ignition points, concluded that with the ascent of the char-making-temperature the semi-coke’s ignition point is getting higher. The test used Coats-Redfern way to study the semi-coke’s activation energy. The result shows the semi-coke’s thermal dynamic model needs two different reaction orders in different temperature. In low temperature the reaction order is n=1; in high temperature it is n=3. When the temperature is low (n=1), the activation energy doesn’t influenced by the heating rate. In high temperature condition the activation energy is getting bigger with the ascent of the heating rate.

Oxygen Ion Transport in Doped Ceria: Effect of Vacancy Trapping

2021 ◽  
Author(s):  
Mehmet Emin Kilic ◽  
Jong-Ho Lee ◽  
Kwang-Ryeol Lee
Keyword(s):  
Oxygen Vacancy ◽  
Ion Transport ◽  
Oxygen Diffusion ◽  
Oxygen Vacancies ◽  
Doped Ceria ◽  
Oxygen Ion ◽  
Vacancy Trapping ◽  
Ceo2 Lattice

Trivalent dopants in CeO2 lattice generate the oxygen vacancies in the lattice, that is vital to oxygen diffusion. However, the dopant also has two detrimental effects on the oxygen vacancy...

Formation and Conductive Properties of Miniaturized Fullerite Sensors

2001 ◽  
Vol 705 ◽  
Author(s):  
Alexander S. Berdinsky ◽  
Dietmar Fink ◽  
Alexander V. Petrov ◽  
Manfred Müller ◽  
Lewis T. Chadderton ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Negative Temperature ◽  
Heavy Ion ◽  
Complex Behaviour ◽  
Ion Tracks ◽  
Temperature Coefficients ◽  
Swift Heavy Ion ◽  
Conductive Properties

AbstractFullerite nanotubules of 100 nm to 2 μm radius, up to 200 nm wal thickness and 10 μm length were produced inside etched swift heavy ion tracks in a polymer, by letting fullerence precipitate from a concentrated C60 solution within the tracks. After contacting the tubules on both sides with silver paste, their resistivity was measured as a function of temperature. All of the 13 prepared samples show a complex behaviour that can be described by tw Arrhenius curves, the low temperature branch with activation energy Eact = (1.77 ± 0.2) eV stemming from pure C60, and the high temperature branch being tentatively ascribed to C60Agx with x ≍ 12.4 and Eact = (0.68 ± 0.2) eV, as the letter compound has found to be produced at ambient temperature by C60 / Ag thermal intermixture. Such samples with tw branches of negative temperature coefficients of resistance might be useful to construct advanced thermoresistors.

EFFECT OF Ni SUBSTITUTION FOR Cu IN THE VORTEX STATE OF (Bi,Pb):2223 SUPERCONDUCTOR

1999 ◽  
Vol 13 (21n22) ◽  
pp. 2775-2782 ◽  
Author(s):  
A. V. POP
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Magnetic Fields ◽  
Temperature Regime ◽  
Vortex State ◽  
Partial Substitution ◽  
High Temperature Regime ◽  
Ni Substitution ◽  
Dissipation Processes

The influence of the partial substitution of x=0.02 Ni for Cu on the magnetoresistivity in the (Bi,Pb):2223 superconductor has been investigated. The resistive transitions were studied under magnetic fields up to 0.7 Tesla by using the dρ/dT versus T curves. The Arrhenius plots shows that the dissipation processes are induced by two distinct regimes. In the high temperature regime the activation energy is proportional to ln B and to B-1 in low temperature regime. The main dissipation processes in these regimes are discussed.

Semiconducting Molybdenum Pyrochlores for high Temperature Applications

1998 ◽  
Vol 512 ◽  
Author(s):  
V. Ponnambalam ◽  
U. V. Varadaraju
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Low Temperature ◽  
Solid Solutions ◽  
Power Factor ◽  
Charge Carriers ◽  
Temperature Range ◽  
Maximum Power Factor ◽  
Increasing Temperature

ABSTRACTThe solid solutions (Y1-xYbx)2Mo2O7 were prepared and the systematic changes in the electrical resistivity (ρ=l/σ), thermopower (S) and power factor (S2σ) have been studied in the temperature range 300–900 K. The lattice parameters ‘a’ and ‘c’ are smaller for higher Yb3+ content phases due to smaller Yb3+ radius and a small tetragonality is observed for all the phases. Semiconducting behaviour is seen for all compositions with systematic increase in activation energy with increasing Yb content. All compositions show negative thermopower indicating electrons are the majority charge carriers in the temperature range of measurements. The calculated power factor values S2σ increase with increasing temperature in the low temperature region and a maximum power factor of ∼0.76×10−7 Wcm−1K−2 is observed at 650K.

Study on Co-Combustion of Oil Shale Semi-Coke and Corn Stalk

2012 ◽  
Vol 614-615 ◽  
pp. 103-106
Author(s):  
Hong Peng Liu ◽  
Wei Yi Li ◽  
Xu Dong Wang ◽  
Hao Xu ◽  
Guan Yi Chen ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Oil Shale ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Corn Stalk ◽  
Kinetics Parameters ◽  
High Temperature Stage ◽  
Blend Ratios

Co-combustion experiment of oil shale semi-coke and corn stalk at different blend ratios was performed using thermogravimetric analyzer. The influence of different blend ratios has been studied. The combustion characteristics are obtained under the heating rates of 20oC/min and the experimental temperature range of 40-850oC. The combustion process of the blends is divided into three stages: low-temperature stage, transition stage and high-temperature stage. With the increasing of corn stalk in the blends, the reaction of combustion mainly shifts from high-temperature stage to low-temperature stage, and there is no obvious change for the ignition temperature, but the burn out temperature comes down. The combustion kinetics parameters of the blends were analyzed using Flynn-Wall-Ozawa model. The result shows that the activation energy of the volatile matter stage increases and the activation energy of semi-coke combustion stage decreases. The combustion characteristics of the oil shale semi-coke get improved significantly with the mixture of corn stalk.

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